Though officially credited solely to Osbourne, "Bark at the Moon" was composed almost entirely by guitarist Jake E. Lee and bassist/lyricist Bob Daisley. Lee claims he was threatened with firing by Osbourne's wife and manager Sharon if he refused to sign a 1983 contract stating that he would relinquish his claims to writing and publishing. In 2003, Daisley filed a lawsuit against the Osbournes, claiming lost royalties for his significant songwriting contributions.
Lyrically, the song deals with a creature of some sort who once terrorized a town, was killed, and later mysteriously returned to once again wreak havoc upon the villagers. The music video, however, borrows heavily from Robert Louis Stevenson's classic Dr. Jekyll and Mr. Hyde story, depicting Osbourne as a "mad scientist" who ingests a substance in his laboratory which causes him to transform into the werewolf depicted on the Bark at the Moon album cover. Thought to be insane, he is subsequently committed to a mental institution.
The music video for the song was partially filmed at the Holloway Sanatorium, outside of London, England. In the early 1980s infancy of the music video medium, the video, which was the first Osbourne had made, was highly anticipated due to his outrageous image. Drummer Tommy Aldridge played on the studio recording of the track, but the video features his replacement in the band, Carmine Appice.